1. Field of the Invention
The present invention relates generally to switches and, more particularly, to battery disconnect switches for preventing undesirable discharge of a battery.
2. Description of the Related Art
A rechargeable battery for use in providing initial energy for starting a motor of a vehicle, such as an automobile, a truck, a bus, a boat and most lawnmowers, is well known. As also well known, once the engine of the vehicle begins to run, an electrical generator provides power to recharge the battery and to energize an electrical load of the vehicle. The electrical load typically includes electrical appliances such as various lights, including safety and illumination lights, power accessories such as power door locks and power windows, and a radio. When the engine of the vehicle is not running, the electrical generator produces no power and the battery becomes the sole source. As most operators have experienced, a substantial risk of over discharging the battery arises when the engine is off and the load has not been disconnected from the battery such as in the case of an automobile where the headlights are left on after the engine has been shut off. In such a case, the battery may be discharged to a level where insufficient power exists to restart the engine of the vehicle--possibly causing the operator to be stranded. In addition, over discharging a battery will shorten the battery life because sulphuration may occur. Sulphuration involves an abnormal sulfate formed on the surface of the battery plates which hinders the battery plate from receiving and accepting a charge because of an increased resistance thereof.
Currently, disconnect switches are available for monitoring the state of the battery and disconnecting the battery from the electric load of the vehicle when the battery is discharging at a high rate or low rate after the engine has been shut off. However, these devices suffer from the draw back that once the battery has been disconnected from the electric load of the vehicle, they must be manually reset by the operator in order to start the engine.